A liquid crystal display device has a gate line formed on a substrate, and a gate insulating film deposited thereon. On the gate insulating film are provided a source line, and a conductive layer above the gate line. An insulating layer is formed thereon, and a pixel electrode is then provided. The conductive layer does not contact the source line, and at least two portions of the conductive layer are electrically connected with the gate line.
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1. A display device having a plurality of pixels, comprising:
a substrate;
a plurality of gate lines provided on the substrate;
a first insulating layer provided on the plurality of gate lines;
a source line at least partially overlapping the plurality of gate lines with the first insulating layer interposed therebetween;
a plurality of island-shaped conductors for repairing source line disconnection, provided below the source line with the first insulating layer interposed therebetween, the plurality of island-shaped conductors provided between and adjacent the gate lines;
a switching element controlling a signal to a pixel;
a second insulating layer with a through hole, provided on the switching element and the plurality of island-shaped conductors; and
a pixel electrode provided above the switching element with the second insulating layer interposed therebetween and connected with the switching element via the through hole, the pixel electrode partially overlapping the plurality of island-shaped conductors.
2. A display device according to
the storage capacitor line provided below the first insulating layer.
3. A display device according to
4. A display device according to
5. A display device according to
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This application is a division of application Ser. No. 10/617,662 (now U.S. Pat. No. 6,958,802), filed on Jul. 14, 2003, which claims the benefit of priority to Japanese Patent Application No. 2002-213335, filed on Jul. 23, 2002, and the contents of application Ser. No. 10/617,662 (now U.S. Pat. No. 6,958,802) are hereby incorporated herein by reference.
1. Field of the Invention
The present invention relates to a method for repairing line disconnection of a display device and a display device capable of repairing line disconnection, which are particularly suitable for application to a liquid crystal display device.
2. Related Background Art
A liquid crystal display device is provided with a matrix of number of signal lines and pixel electrodes. As the number of signal lines is on the increase because of the recent trend of larger and higher resolution liquid crystal display devices, the problem of line disconnection can occur more often. Line disconnection occurs due to pinholes and dust in the manufacturing process. In the event of disconnection, a proper voltage is not applied to a pixel electrode corresponding to a disconnected line, causing line defects and other display problems to produce a defective product. Therefore, a method for repairing line disconnection using a laser is now under research and development.
The active matrix liquid crystal display device shown in
A method for repairing signal line disconnection is described in Japanese Patent Application Laid-Open No. H09-113930, for example. The method according to the first embodiment of the above prior art will be explained hereinbelow.
As shown in
As shown in
As shown in
In the following, a description will be given on the case where the gate line 15 is disconnected. As shown in
Disconnection of the gate line 15, the storage capacitor line 16, and the source line 17 occurs due to pinholes and dust in the manufacturing process. If the disconnection occurs, no drive signal is given to the pixel, thus disabling display.
The case where disconnection occurs at the disconnected portion 28 of the gate line 15 of an active matrix liquid crystal display device will be explained hereinbelow. A laser is applied to the positions at both outsides of the disconnected portion 28 (the positions shown by the cross marks in
Disconnection of the source line 17 can be also repaired in the same way as shown in
The above conventional technique, however, has the following problems. In the first embodiment of the invention disclosed in Japanese Patent Application Laid-Open No. H09-113930, the connection resistance of the pixel electrode 12 and the molten metal 29 can be high. The pixel electrode 12 is formed by Indium Tin Oxide (ITO), and the connection resistance with chromium, tantalum, titanium, and molybdenum used for the gate line 15 and the storage capacitor line 16 significantly differs depending on conditions of film deposition and film surface. There is a case where the connection resistance reaches several megohms, which results in decrease in the rate of successful repair. Use of aluminum for the gate line 15 is especially problematic since the connection resistance of an aluminum element and ITO used for the pixel electrode 12 is extremely high. Therefore, when a laser is applied to connect them, the connection electrical resistance almost reaches one megohm, which is above the limit of the connection resistance for repairing disconnection. Besides, the application of a laser to the pixel electrode 12 causes the ITO to be peeled off and a fragment of the ITO is stuck in between a counter electrode and the pixel electrode to trigger unexpected short-circuit.
The repair method described in the second embodiment of the invention disclosed in Japanese Patent Application Laid-Open No. H09-113930 also has problems. According to the method, the conductive layer for repairing line disconnection is additionally provided on the pixel electrode 12. Therefore, the manufacturing process requires an additional step of forming the conductive layer. Also, the conductive layer is placed on the pixel electrode applying an electric field to liquid crystals. Therefore, after the repair, an electric potential of a source signal, gate signal, or common signal is directly applied to the liquid crystals through the conductive layer. It causes noise to have an adverse effect on operations of the liquid crystals, resulting in poor display quality.
As described above, the conventional method for repairing line disconnection has the problems of a reduced rate of successful repair and deteriorated display quality caused by an expected short-circuit and noise.
The present invention has been accomplished to solve the above problems and an object of the present invention is thus to provide a display device capable of repairing line disconnection without decreasing display quality, and the repair method.
A display device according to the present invention is a display device having a plurality of pixels, including a substrate; a conductive line provided on the substrate; a first insulating layer provided on the conductive line; an island-shaped conductor for repairing line disconnection, provided above the conductive line with the first insulating layer interposed therebetween; a switching element controlling a signal to a pixel; a second insulating layer with a through hole, provided on the switching element and the island-shaped conductor; and a pixel electrode provided above the switching element with the second insulating layer interposed therebetween and connected with the switching element via the through hole. In this configuration, the display device is capable of repairing line disconnection without decreasing display quality.
In the above display device, the conductive line can be a gate line transmitting a control signal to the switching element.
The above display device can also include a source line provided in the same layer as the island-shaped conductor.
In the display device, the conductive line can be a storage capacitor line forming a storage capacitor with the pixel electrode.
The above display device can also include a source line provided in the same layer as the island-shaped conductor.
It is also possible in the display device that a plurality of island-shaped conductors are provided above the conductive line.
It is preferable in the display device that at least two portions of the island-shaped conductor are connected to the conductive line.
In the display device, the island-shaped conductor and the conductive line can be connected by laser application.
Another display device according to the present invention is a display device having a plurality of pixels, including a substrate; a first insulating layer provided on the substrate; a conductive line provided on the first insulating layer; an island-shaped conductor for repairing line disconnection, provided below the conductive line with the first insulating layer interposed therebetween; a switching element controlling a signal to a pixel; a second insulating layer with a through hole, provided on the switching element and the conductive line; and a pixel electrode provided above the switching element with the second insulating layer interposed therebetween and connected with the switching element via the through hole. In this configuration, the display device is capable of repairing line disconnection without decreasing display quality.
In the above display device, the conductive line can be a source line transmitting a display signal to the switching element.
It is also possible in the display device that a plurality of island-shaped conductors are provided above the conductive line.
It is preferable in the display device that at least two portions of the island-shaped conductor are connected to the conductive line.
The display device can also include a gate line provided in the same layer as the island-shaped conductor, the gate line transmitting a control signal to the switching element.
The above display device can also include an island-shaped conductor for repairing gate line disconnection provided in the same layer as the source line, above the gate line.
The display device can also include a gate line and a storage capacitor line provided in the same layer as the island-shaped conductor, the gate line transmitting a control signal to the switching element, and the storage capacitor line forming a storage capacitor with the pixel electrode.
The above display device can also include an island-shaped conductor for repairing gate line disconnection provided in the same layer as the source line, above the gate line; and an island-shaped conductor for repairing storage capacitor line disconnection provided in the same layer as the source line, above the storage capacitor line.
A method for repairing a display device having a plurality of pixels according to the present invention is a method including a step of preparing a display device, the display device having a substrate, a conductive line layer provided on the substrate, an island-shaped conductor for repairing line disconnection, the island-shaped conductor overlapping with the conductive line layer, a first insulating layer provided between the island-shaped conductor and the conductive line layer, a switching element controlling a signal to a pixel, a second insulating layer with a through hole, provided on the switching element, and a pixel electrode provided above the switching element and the island-shaped conductor with the second insulating layer interposed therebetween and connected with the switching element via the through hole; a step of applying a laser to two points across a disconnected portion of the conductive line layer; and a step of connecting the island-shaped conductor and the conductive line layer at the two points by applying a laser. This method is capable of repairing line disconnection of the display device without decreasing display quality.
In the above method, the island-shaped conductor can be provided above the conductive line layer.
In the method, on the other hand, the island-shaped conductor can be provided below the conductive line layer.
In the step of applying a laser in the above method, the laser can be applied from the side of the substrate.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
First Embodiment
A method for repairing line disconnection according to the present invention will be explained hereinafter with reference to
As shown in
Next, the first n+ silicon film 25 and the second n+ silicon film 26 are formed in isolation from each other. On the second n+ silicon film 26 is formed the source electrode 27, the two electrically connected. On the first n+ silicon film 25 is the drain electrode 14, electrically connected. The first n+ silicon film 25 and the second n+ silicon film 26 are formed by doping the silicon semiconductor layer 23 with impurities such as P and As. It is therefore possible to form the first n+ silicon film 25 and the second n+silicon film 26 in the same step. The drain electrode 14 and the source electrode 27 are deposited by sputtering, and patterned by the photolithography process.
Then, the contact hole 30 is formed on the insulating film 45 to electrically connect the pixel electrode 12 and the drain electrode 14. The contact hole 30 is formed in the process of resist coating, exposure, development, etching, resist stripping, and so on. The pixel electrode 12 is formed thereon by depositing ITO by sputtering to have electrical connection with the drain electrode 14. The conductive layer 41 according to the present embodiment can be formed in the same layer as the drain electrode shown in
If a laser is applied from the side of the pixel electrode 12, on the other hand, electrical continuity is provided between the pixel electrode 12 and the gate line 15 as shown in
The connection resistance of the molten metal 29 and the pixel electrode 12 is substantially the same as the connection resistance of the pixel electrode 12 and the drain electrode 14 through the contact hole 30 composed of the same material. Further, the electrical resistance can be kept within 100 k Ω that is sufficient value for the repair, thus increasing the repair rate. The conductive layer 41 can be formed and patterned in the same layer as the source line 17 and the drain electrode 14. Therefore, the conductive layer 41 is formed by sputtering chromium, tantalum, titanium, aluminum, molybdenum, and the like. The conductive layer 41 has to lie over the disconnected portion 28, and therefore it is preferably as large as possible without contacting the source line 17 for a larger repairable area.
Second Embodiment
A method for repairing line disconnection according to the second embodiment of the present invention will be explained hereinbelow with reference to
Below the pixel electrode 12, a pair of the conductive layers 41, a pair of the conductive layers 42, and a pair of the conductive layers 43 are formed in an island shape above the gate line 15, the storage capacitor line 16, and the source line 17, respectively. The conductive layers are electrically floating. In the first embodiment, the conductive layer is provided in a possibly larger area on each of the three lines surrounding one pixel. In the second embodiment, on the other hand, each of the pair of the conductive layers is provided at each end of the three lines. The conductive layers above the gate line 15 and the storage capacitor line 16 can be formed in the same layer as the drain electrode 14 shown in
The connection resistance of an aluminum element and ITO used for the pixel electrode 12 is extremely high. The repair of the gate line 15 in the conventional liquid crystal display device results in the cross-section structure shown in
Other Embodiments
The method for repairing line disconnection and the structure therefor described in the above first and second embodiments are also applicable to the repair of disconnection of the source line 17 and the storage capacitor line 16. In the repair of disconnection of the source line 17, the conductive layer 43 can be formed in the same layer as the gate line 15; therefore, no extra manufacturing step is needed to maintain productivity. The conductive layer 43 is deposited by sputtering as with the case with the gate line 15. A laser is applied from the backside of the substrate 11 (the side where the TFT is not provided) to avoid contact between the pixel electrode 12 and the molten metal 29. The repair of the line disconnection is thereby attained without generating a point defect.
If the storage capacitor line 16 is provided between the gate lines 15 as shown in
In the repair of the storage capacitor line 16, the conductive layer 42 can be formed in the same layer as the source line 17 as with the case with the gate line 15. No extra manufacturing step is therefore required. The conductive layer 42 has to avoid electrical contact with the adjoining source line 17. The conductive layer 42 is preferably as large as possible to obtain a larger repairable area.
If the repair results in direct contact between the conductive layer and the pixel electrode 12 and signals are directly applied to the pixel electrode 12, it is preferable to apply a laser to the cut line 50 on the TFT so as to separate the pixel from the TFT as shown in
The present invention is particularly effective when applied to an active matrix liquid crystal display device in which a gate line and a source line cross each other with a gate insulating film therebetween. The present invention is also applicable to a liquid crystal display device further having a storage capacitor line parallel to the gate line. Further, the present invention can be applied to a liquid crystal display device of In-Plane-Switching (IPS) mode having comb-shaped electrode pairs comprised of a plurality of electrodes to apply an electric field horizontally causing liquid crystal molecules to rotate parallel to a substrate. Furthermore, the present invention can be applied to a display device other than a liquid crystal display device, having two kinds of lines crossing each other with an insulating film therebetween.
As explained in the foregoing, the present invention provides a display device capable of repairing line disconnection without decreasing display quality, and the repair method.
From the invention thus described, it will be obvious that the embodiments of the invention may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended for inclusion within the scope of the following claims.
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